Princess is the feminine form of prince (from Latinprinceps, meaning principal citizen). Most often, the term
has been used for the consort of a prince, or his daughters.

For many centuries, the title "princess" was not regularly used
for a monarch's daughter, who might simply be called "Lady" or a
non-English equivalent; Old English
had no female equivalent to "prince", "earl", or any royal or noble
aside from the queen, and the women of nobility bore the title of
"Lady".

As women have slowly gained more autonomy through European
history, the title of princess has become simply the female
counterpart of prince and does not necessarily imply being
controlled or owned by a prince. In some cases then, a princess is
the female hereditary head of state of a province or other
significant area in her own right. The ancient meaning applies in
Europe still to the extent that a female commoner who marries a
prince will almost always become a princess, but a male commoner
who marries a princess will almost never become a prince, unless
his wife has, or is expected to attain, a higher title, such as Queen regnant. The
implication is that if the man held the equivalent masculine title,
he would have rank over his wife without the necessary pedigree.

In many of Europe's royal families, a king would grant his heirs actual or
theoretical principalities to train them for future kingship or to
give them social
class. This practice has led over time to many people thinking
that "prince" and "princess" are titles reserved for the immediate
family of a king or queen. In fact, most princesses in history were
not immediate members of a royal family but women who married into
it; however, in many cases, a princess would choose someone outside
of royalty to wed.

A princess is a female member of a royalfamily, especially a daughter of a monarch. A son of a monarch is called a prince. In some cases a woman can become a princess by marrying a king.
A princess may also become a ruler by heredity or by marriage.
Sometimes the expression "princess" is used when a female has noble qualities such as kindness, charity, and virtue.